You should download and read Demonstration #4 - STAR configuration and Demonstration #5 - 80M, 40M, 20M EH antennas (download Demonstration # 4 or #5 from here).I built most of my EH antennas out of commonly available parts (PVC pipe and aluminum roofing flashing). These materials are inexpensive and can be purchase at most hardware stores.The diagram below illustrates a basic form of the STAR EH antenna. It consists of two cylinders and three coils. The spacing is related to the diameter of the cylinder.
20M EH - 2” PVC
Information and data on this page is from documentation obtained from the EH web site and from my own experience with building these antennas.
Depending on the size of the antenna I usually build each section separately and then glue them together to form a complete antenna. In this manner I have smaller pieces to work with and it is easier to run wire down the inside of the cylinders. For smaller antennas just build the antenna in one piece. Below is a picture of an 80M EH antenna illustrating the separate pieces. PVC pipe comes in different sizes (nominal pipe sizes - same as water pipe). Use PVC and not CPVC (for hot water) also don’t use grey conduit as it absorbs RF and will break down under high voltage. PVC pipe comes in different thickness do not use the thin wall except on 3” or larger pipe. Schedule 40 and thin wall pipe is usually what is stocked in local hardware stores, use Sch. 40 for 2” and smaller diameter piping.
What Band is the Antenna Design for: The frequency band will determine the ration of the cylinder lengths to diameter. For 80M and 40M you will probably want a high angle of radiation, so select a ratio of 10 - 14. On the other bands you will most likely be looking for DX so the ratio should be 3 - 5. What Diameter of pipe are you going to use: The larger the pipe, the larger the bandwidth. For a 20M antenna you can go with 1” pipe or larger. For 40M or 80M you should probably go with 2” or larger pipe. What Materials are you going to use to construct your cylinders? Copper foil from the craft supply store is a favorite but, is not too weather resistant. One inch copper pipe can also be used fut it is more expensive than other materials. The one in copper pipe can fit over 3/4” PVC pipe if it is sanded down a slight bit. I use aluminum roofing flashing and secure it with sheet metal screws every 2 - 3 inches. I overlap the end by 1”, this makes the width of the flashing 8 1/2” for 2” PVC pipe. Flashing comes in 10”, 12”, and 18” widths. What kind of wire are you going to use? I usually use # 14 enamel wire. Some of the guys use # 12 insulated house wiring. Both of these are adequate for 100 watts. Some of the guys are using the center conductor of RG-8 for wiring between the top cylinder and the coil (remove the outside shield and just use the center conductor and the insulation - reduces the chances of arcing).
We will design a 20M STAR EH antenna using 2” PVC with aluminum flashing and # 14 wire. Using the PVC pipe dimension chart above you have a diameter of 2.375”. For 20M you would want a ratio of 3 so the cylinder would be 3 X 2.375 = 7.125”. So let’s use 7 1/4” (makes it easier to measure - it is not too critical).you will need a piece of 2” PVC Sch. 40 pipe. I always leave myself a little room for mistakes soI would get a piece 3 foot long (2 * 7 1/2”=15 +3” (between cylinders)+ 6” for coils = 24”). PVC pipe comes in standard 10’ lengths. Some stores will have 5’ pieces already cut for you, but check the price as the cut pieces are about 80% of the cost of the 10’ piece. You will also need two couplings - in 2” PVC they have long ones and shore ones - get the short. Aluminum flashing (look in the roofing section) comes in different widths, 10”, 12” & 18”. You will have to buy a roll (it come in different lengths also - get the shortest roll - 10’). You will need a piece about 8 1/2” X 15”.Download the Coils Design spreadsheet and enter your data (cylinder diameter [diameter of PVC pipe], the cylinder lengths, frequency, and type of wire). It will then give you the number of turns required for the two coils (Phasing and tuning coil - the source coil will be determined after the initial tuning. It calculates that you need 10 turns on the tuning coil - make it 12 or 13 so you can have some tuning (it is a lot easier to remove turns than to add them).